build: bump certifi from 2019.3.9 to 2019.6.16 (#1543)
build: bump certifi from 2019.3.9 to 2019.6.16 (#1543)

Bumps [certifi](https://github.com/certifi/python-certifi) from 2019.3.9 to 2019.6.16.
- [Release notes](https://github.com/certifi/python-certifi/releases)
- [Commits](https://github.com/certifi/python-certifi/compare/2019.03.09...2019.06.16)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
skylines-project/skylines,skylines-project/skylines,skylines-project/skylines,skylines-project/skylines